Theoretical Methods for Supramolecular Chemistry

Also, various spectroscopic quantities can be calculated in order to test experimental assumptions Once a structure of a supramolecular assembly has been assumed, optimized or propagated in time, properties like vibrational frequencies, infrared, Raman [93], or Resonance Raman [159] intensities, NMR or EPR parameters can be calculated with first-principles methods to be compared with the experimentally measured spectra in order to confirm or reject the structural basis assumed in the interpretation of the experimental spectra. It is impossible to review the work and achievements of theoretical chemistry in this respect. Therefore, we concentrate on selected examples in the following. The interested reader is referred to the book by Kaupp, Biihl and Malkin [160] for the calculation of NMR and ESR parameters and to Refs. [161, 162] for more general discussions of molecular property calculations. NMR parameters are molecular properties probed at atomic nuclei and thus ideal for linear-scaling or empirical approaches. An efficient linear-scaling method for supramolecular systems has been presented recently [163]. 

A good qualitative insight into the transitions involved in the color change of sensors can usually be obtained from density functional theory (DFT) and other theoretical methods that have proved to be a very accurate tool for theoretical studies in supramolecular chemistry.DFT appears to be a reasonably accurate theoretical method that is both widely available in various software packages and can be run on personal computers, that is, does not necessarily require Unix or Unix-like environments, servers, and so on. On the other hand, multireference configuration interaction methods typically offer accuracies of about 0.1 eV... 

The active development of computational methods aimed at molecular design [1.38-1.41] provides a means for building up a theoretical supramolecular chemistry of not only explicative but also predictive power. Significant insight has already been gained and much more may be expected from the interplay of theory and experiment in the study of supramolecular features (interactions, structures, dynamics, association constants, medium effects, etc.) [1.35, 1.42-1.50, A.37]. 

The theoretical study of supramolecular systems has certainly just begun. Tlte technical means for such studies have been provided within the last decades. In the future, these methods will be improved and refined. Also new approaches will be envisaged, which are tailored for the specific purposes of supramolecular chemistry - some of which have already been discussed in this work. 

The authors suggest that computational chemistry offers the necessary tools to predict cluster energies associated with molecules designed for aggregation on the drawing board and we have seen that this goal has practically been achieved in the meantime. Furthermore, they stress, that tools to predict conformational trends are required, and argued that, therefore, the refinement of molecular force fields via quantum chemistry and the developments of better minimization techniques could be a major contribution. We hope that we have elaborated on these propositions in this account and that we were able to draw a more complete picture of what theoretical methods are capable of and into which directions they should evolve when the focus will be supramolecular chemistry. 

In the last 130 years, chemistry has focused its attention on the behavior of molecules and their construction from the atoms. Atoms are held together in molecules by chemical bonds [1]. This is within the framework of the theoretical of atoms-in-molecules. From a modem point of view, the chemical bond has been designed using theoretical methods based on the quantum mechanical ab initio for molecules isolated with high accuracy by comparing the results with high-resolution spectroscopies [2, 3]. The basic and fundamental unit that we call molecule is interpreted with some detail. However, in the last three decades chemists have moved beyond the atomic and molecular chemistry towards the area of supramolecular chemistry [4—6]. This new area is in the central part of the bottom-up approaches to... 

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